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Commit 58b32c1b authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo
Browse files

perf python: Make twatch.py use soft dummy event, freq=0 



To not sample, what we want are just the PERF_RECORD_ lifetime events
for threads, using the default, PERF_TYPE_HARDWARE +
PERF_COUNT_HW_CYCLES and freq=1 (the default), makes perf reenable
irq_vectors:local_timer_entry, disabling nohz, not good for some use
cases where all we want is to get notifications when threads comes and
goes...

Fix it by using PERF_TYPE_SOFTWARE (no counter rotation) and
PERF_COUNT_SW_DUMMY (created by Adrian so that we could have access to
those PERF_RECORD_ goodies).

Reported-by: default avatarLuiz Fernando Capitulino <lcapitulino@redhat.com>
Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jaroslav Skarvada <jskarvad@redhat.com>
Cc: Jeremy Eder <jeder@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-kfsijirfrs6xfhkcdxeoen06@git.kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 84576da2

tools/perf/python/twatch.py

+11 −1
Original line number Diff line number Diff line
@@ -18,10 +18,20 @@ import perf 
def main():

	cpus = perf.cpu_map()

	threads = perf.thread_map()

	evsel = perf.evsel(task = 1, comm = 1, mmap = 0,

	evsel = perf.evsel(type	  = perf.TYPE_SOFTWARE,

			   config = perf.COUNT_SW_DUMMY,

			   task = 1, comm = 1, mmap = 0, freq = 0,

			   wakeup_events = 1, watermark = 1,

			   sample_id_all = 1,

			   sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU)



	"""What we want are just the PERF_RECORD_ lifetime events for threads,

	 using the default, PERF_TYPE_HARDWARE + PERF_COUNT_HW_CYCLES & freq=1

	 (the default), makes perf reenable irq_vectors:local_timer_entry, when

	 disabling nohz, not good for some use cases where all we want is to get

	 threads comes and goes... So use (perf.TYPE_SOFTWARE, perf_COUNT_SW_DUMMY,

	 freq=0) instead."""



	evsel.open(cpus = cpus, threads = threads);

	evlist = perf.evlist(cpus, threads)

	evlist.add(evsel)